The orbital office complex is the space station from where
Kirk and Scotty start their tour of the newly refitted Enterprise in "Star Trek: The
Motion Picture". After the movie the miniature was redressed and showed up several more
times. These are the appearances in chronological order:

The following analysis identifies three variants of the
model and comments on the depictions published in the Star Trek Fact Files.

Orbital
office complex The orbital office complex is composed of four long
brownish tubes occupying the upper two thirds of the station, a number of arms with smaller and larger
round pods around the center (some of which seem to be still under construction)
and a cone-shaped lower section. Each of the
disks in the center part is clearly just one deck tall, as evidenced by the
window sizes as well as by the shots of the undocking travel pod. This gives us a diameter
of just around 200m across its wide side.

The orbital office complex is reproduced largely correctly
in the Star Trek Fact Files. The drawing is obviously closely based on actual model photos, the only notable inaccuracy is that a ball-like
structure at the very bottom of the station does not exist, so we removed it.

Regula
type When the miniature was slated to appear in "Star Trek: The Wrath of
Khan" as the Regula One lab, it was turned upside down as the most obvious
"alteration". In addition, the structure looking like an antenna dish at
the bottom (former top) was removed, together with the clamps that were holding
the big tubes and the antenna together. The now lower clamps are still present
on the Fact Files depiction, however. While all four of the tubes of the
orbital office complex are brown, two of them are beige on the Regula lab. The new top is adorned by
an antenna
spire. All of the smaller pods were removed from the outriggers on the wide side, leaving only
the four largest ones
and two smaller ones between the large pods on the narrow side of the station.
One of the larger pods now holds what is obviously an observatory dome, possibly
the one that was still under construction on the orbital office complex. Finally
there is a less obvious modification which was not included in the Fact Files
drawing. Rectangular structures looking like solar panels are affixed to all
four sides of the conical top section of Regula One.

After probably six years in storage the miniature was
unearthed for a couple of TNG episodes. Without any visible modifications it
appears in TNG: "The Child", here acting as a science station that may
easily be of an identical or similar type as Regula One. When the model is seen
in TNG: "The Measure of a Man", still without any changes, it
represents a large starbase, and the blatant scaling error becomes obvious
comparing the station's windows to those of the Enterprise-D. Here the upper dome
of the station alone measures more than 1000m across.

In TNG: "A Matter of Perspective" we see a small
Regula-type station as well. At least, it would make sense for Dr. Apgar's
research station to be that small. Another appearance of the model in its Regula
version is in TNG: "Parallels", albeit only on a display as Deep Space
5. Finally we can see the miniature, for the last time with the tubes, in DS9:
"Blaze of Glory". The unnamed starbase is the place where Eddington is
imprisoned. But this is just stock footage of Regula One from "Star Trek
II".

Starbase
type The model was modified one last time to represent Starbase 375
in a number of DS9 episodes. The four tubes were removed, but once again nothing
was done to support the definitely much larger size of the Starbase relative to
the orbital office complex. There is one more change to miniature, however. On
one side, the one with the observatory, the small pod was removed. The latter
may have happened earlier, when the tubes were still present, but it is
unmistakably visible only as late as on Starbase 375. As for the station's size,
a 120m Defiant would give us a diameter of around 500m for the head section.

Note The
"official" EAS rendition on the right has partitioned windows in
order to make this variant of the station look bigger.

Starbase 257 (DS9: "Valiant") is
identical to Starbase 375 - only stock footage was used. Finally, in VOY:
"The Omega Directive" the station turns up on a computer screen as the
secret Federation research outpost that was destroyed by the Omega Molecule,
surprisingly yet again without the tubes - although the image is
computer-generated and although this station may have been intended to be small.

The two versions called "Regula type" and
"Starbase type" were not consistently used as small science stations
and as huge starbases, respectively. But even if we accept that, it is hard to
overlook the scaling error that arises from the way too large windows of the
miniature. Still, there is no convenient way of ignoring that the large version
exists as it could be seen several times in direct comparison with the
Enterprise-D, the Defiant, a Jem'Hadar fighter and other ships.

Here is a table with all versions and appearances of the miniature at
a glance: